Rotary rheostat



R. W. EBELING.

ROTARY RHEOSTAT.

APPLICATION FILED SEPT. III. I9I7.

Paented Nov. 25, 1919.

UNITED STATES PATENT OFFICE.

ROBERT W. EBELING, OF OAKLAND, CALIFORNIA, AgSIGNOR TO R. W. EBELING COMPANY, INCORPORATED, A CORPORATION OF CALIFORNIA.

ROTARY nHEosTAT.

Application filed September 18, 1917.

To all lwhom z't may concern:

Be it known that I, ROBERT W. EBELING, citizen of the United States, residing at Oakland, in the county of Alameda and State of California, have invented certain new and useful Improvements in Rotary Rheostats, of which the -following is a specification.

The present invention relates to improvements 1n means for controlling the amount of current applied to an electric circuit. It relates more specifically to means whereby the resistance of two cordinated circuits may be varied to any predetermined amount 0r degree.

The inventionl has for its object the provision of means for the dimming or the brightening of incandescent colored lights, such as are used in electric signs, spotlights or stereopticon projectors where it is desired to blend colors or make secondary colors by varying the intensity of primary colors, one primary fading at the same ratio that the opposed one is brightened and vice versa.

The invention will be hereinafter fully set forth and particularly pointed out in the claims.

In the accompanying drawings:

Figure 1 is a vertical central section of my' improved rotary rheostat. Fig. 2 is a vertical side view of saine on a scale onehalf that of Fig. 1. Fig. 3 is a view of a modified detail. Fig. l is a view of another modification of same detail.

Referrin to the drawings, 1 indicates a base of a ox; or housing having two end walls 2, two side walls 3 and a top or closure 4. The side walls 3 have in their centers holes for bearings 6, in which are rotatably mounted hollow shafts 7, integral with a lcoupling' 8, made of any suitable insulative material. The upper and lower faces/ of said coupling are provided with projecting bosses threaded to receive the inner ends of cylindrical cells 9 and 11, respectively, the

I.opposite ends of which are internally threaded, to receive plugs 12, of insulative material.

Extending through the centers of the plugs 12 are the ends of graphite resistance units 13, each having a binding post 1a and thumb nut 16 thereon, both of the usual construction for connection with one wire of a circuit. The other wires of the respective Specification of Letters Patent.

Patented Nov. 25, 1919.

serial No. 191,952.

circuits are connected to similar posts 17 in the side walls of the cells 9 and 11.

The coupling 8 has two ports 18 and 19, connecting the interiors of the cells 9 and 11. The said ports are tapped to receive ends of pipes 21 and 22, which extend in opposite directions from the coupling 8 into the respective cells.

Extending inwardly through the shaft 7, longitudinally through the central portion of the coupling 8, and rotatable therein, is a valve stem 23, having a controlling handle 24. In the said valve stem 23, are ports 26 and 27, arranged to coincide with the ports 18 and 19, and intended tol register therewith normally, and to regulate the size of said ports when the valve stem 23 is rotated. In one of the plugs 12 is a port 28 tapped to receive the threaded end of a plug 29.

It will be seen from this construction that the device comprises in effect two separate air-tight cells which are rotatable on'a common axis. The valve stem 23 affords communication between the two whenl desired. In operation the plug 29 is removed, and a quantity of mercury 31, sufficient. to nearly fill one cell, is poured into the cell. The plug 29 is replaced and the-valve stem 23 turned to open the ports 18 and 19. In the portion shown in Fig. 1, the mercury 31 gravitates through port 19, and the air which is displaced thereby, ascends through port 18. When the device is rotated onehalf revolution, the mercury is again in the upper cell and the gravitation process repeated, the said'mercury receding on the resistance cone above and advancing on the one below.

It is obvious that the amount of resistance offered by the coneJ of graphite is determined by the level of the mercury which shorts the circuit between the connection on the posts 14 and 17. A progressive degree of resistance is obtained by reason of the tapered or conical shape of the unit 13.

Assuming that there are two colored incandescent lights as of a spotlight focused on the same surface, each light having its resistance cone in one of the cells 9 or 11, then it is desired to diminish one color and produce another. This can be accomplished in the following manner:

It will be seen that but one light will be burning when the device is in a normal vertical position, as illustrated in Fig. 1.

The device may be rotated one-quarter turn with no diminution of the resultant projected light, but Iimmediately upon a complete reversal, the mercury starts to drain from the full cell into the empty one, and

4gradually bring in the light having its resistancein the lower cell at the same time dimming the one above, until the mercury in the upper cell reaches a level lower than that of the bottom of the upper resistance cone, when the light on that circuit is out. The change from one color to another in this way is brought about gradually without the transition being abrupt or perceptible.

In Fig.. 3 I have shown a modified form of my graphite resistance cone. In this case it is made conical, the angle of the sides determining the speed of reduction of resistance as the mercury advances or recedes on its surface.

In Fig. 4 I have shown another form of resistance unit. `In this case its surfaces are ,l lmade to conform to a typical curve or chart reading corresponding to the exact ratio of reduction desired for a given effect.

The oscillation of the cells may be accomplished by means of a crank 32, secured to the shaft 7, or by a rack 33', slidable in bearings 35, and having a finger hole 34. The said rack 33 meshes with a pinion 36, keyed to the shaft 7 as shown at 38.

Having thus explained the nature of the invention and described an operative manner of constructing and using the same, although without attempting to set forth all of the forms in which it maybe made, or all of the methods of its use, the following is claimed l. An improvement in means for controlling electric currents comprising a rotatable shaft, radially disposed cells supported by said shaft and communicating with each other, each cell having a resistance element therein, a conducting liquid confined within said cells'and free to flow from one cell to another when said shaft has been rotated,

f whereby the resistance element in the cell receiving the inflowing liquid is submerged by the liquid and the resistance element in the other cell is exposed by theoutow of liquid therefrom.

2. An improvement in means for controlling electric currents comprising a rotatable shaft, radially disposed cells supported by said shaft and communicating with each other, each cell having a resistance element therein, a conducting liquid confined within said cells and free to flow from one cell to another when said shaft has been rotated, whereby the infiowing liquid will submerge a resistance element and another resistance element will be uncovered by the outflowingliquid, and means controlling the flow of said liquid.

3., An improvement in means for controlling electric currents comprising a rotatable shaft, radially disposed cells supported by said shaft, said shaft having passagesextending therethrough and communicating with oppositely disposed cells, each cell having a resistance element therein, and a conducting liquid conined within said cells and free to flow from one cell to another through said passages, when said shaft has been rotated, whereby the inowing liquid will submerge a resistance element and another resistance element is uncovered by outflowing liquid.

4. An improvement in means for controlling electrical currents comprising a rotatable shaft having radial passages extending therethrough, radially disposed cells supported by said shaft and communicating with each other through said passages, a rotatable valve within said shaft controlling said passages, resistance elements within the respective cells, and a conducting liquid free to flow from one cell to another through said passages when said shaft has been rotated, whereby the inflowing liquid will submerge a resistance element and another resistance element will be uncovered by outflowing liquid.

5. An improvement in means for controlling electric currents comprising a rotatable shaft, radially disposed cells supported by said shaft and communicating with each other, each cell having a resistance therein having means whereby the degree of resistance may be progressively varied, and a conducting liquid free to flow from one cell to another when said shaft has been rotated, whereby the inflowing liquid will submerge a resistance element and another resistance element will be uncovered by outflowing liquid.

6. An improvement in means for controlling electric currents comprising a rotatable shaft, radially disposed cells supported by said shaft and communicating with each other, each cell having a resistance element v therein composed of a tapered body of conducting material, and a conducting liquid free to flow from one cell to another when said shaft has been rotated, whereby the inflowing liquid will submerge a resistance element and another resistance element will be uncovered by outflowing liquid.

7 An improvement in means for controlling electric currents comprising a rotatable shaft provided with radially disposed passages extending therethrough, radially disposed cells supported by said shaft, tubes extending from the respective passages to the outer ends of the respective cells, whereby communication between the cells is established, resistance elements within the respective cells, and a conducing liquid free to flow from one cell to another through said passages and tubes when the shaft has been rotated, wherebythe inowing liquid will submerge aresistance element and another resistance element will be uncovered by outflowing liquid.

8. An improvement, in means forcontrolling electric currents comprising a rotatable shaft provided with radially disposed bosses, tubular members attached to said bosses and forming radially disposed cells, means being provided whereby said cells are placed in communication with each other, resistance elements within the respective cells, and la conducting liquid free to flow `from one cell to another when said shaft has been rotated, whereby the infiowing liquid will submerge a resistance element and another resistance element will be uncovered by outflowing liquid.

9. An improvement in means for controlling electric currents comprising a rotatable shaft provided with radially disposed bosses having passages therein, a valve shaft rotatable within said shaft and having passages positioned to coincide with the first named passages, tubular members attached to saidbosses and forming radially dis-k posed cells conununicating with each other through said,l passages, resistance elements Within the respective cells, and a conducting iuid free to low from one cell to another through said passages, whereby the infiowing liquid will submerge a resistance element and another resistance element will be uncovered by outl'lowing liquid.

10. An improvement in means for controllingelectric currents comprising a rotatable shaft provided with radially disposed tubular'cells communicating with each other, plugs removably mounted in the outer ends of said tubular cells andlclosing the same, resistance elements carried by said plugs and extending into said cells,v and a conducting' liquid free to flow from one cell to another, whereby the infiowing liquid will submerge a resistance element andanother resistance element will be, uncoveredl by outiowing liquid.

ln testimony whereof I aiX my signature.

ROBERT W. EBELING. 

